CHEMICAL DYNAMICS OF ANIMAL NUTRITION 127 



The latter of these hypotheses seemed the more likely, and in 

 the second paper on the subject of autolysis, it was suggested that the 

 tissue stability of the liver was the resultant of the mass action of three 

 sets of bodies, viz., the tissue itself, the metabolites, or bodies derived 

 from metabolites, and the autolytic enzyme. 



The following immediate questions then arose : (i) In what way 

 do the metabolites act ? Do the products of tryptic digestion them- 

 selves inhibit the action of the autolytic enzyme, or is it the products 

 derived therefrom which exert this inhibitory action ? (ii) If such 

 metabolites, or bodies derived therefrom, exert an action in the 

 manner suggested, are they continually circulating in the blood-stream, 

 or are they taken up in the tissues and acting intracellularly ? 



To obtain an answer to question (i) the influence of glucose, and 

 of the products of tryptic digestion of caseine on the rate of autolysis 

 of the liver were determined. For an answer to question (ii) the 

 relative inhibitory action of sera from fed and fasting animals on 

 autolysis was investigated. As a result of these experiments it was 

 found that glucose exerted no action on the rate of autolysis, whereas 

 the products of tryptic digestion exerted a marked inhibitory effect. 



In the experiments on the action of sera, it was found that in 

 one series no difference could be detected between the influence 

 exerted by the serum of a fasting animal and that of a 

 fed animal ; in a second series, however, the inhibitory 

 action of the serum of a fed animal was slightly greater. In 

 this second series, the serum contained a larger amount of un- 

 coagulable nitrogenous bodies. All experiments were carried out with 

 sera diluted with a triple volume of normal saline. 



As the result of the above-mentioned preliminary experiments, 

 the question as to whether the products of tryptic digestion circulate 

 in the. organism acquires additional importance. That they inhibit 

 autolysis there is little doubt : on the other hand experiments carried 

 out with sera do not conclusively prove that the serum of a fed animal 

 contains these products in quantity sufficient to shew a greater 

 inhibitory power than the serum of a fasting animal. 



